Objective: Chronic fatigue syndrome (CFS) patients report usually cognitive complaints. They also have frequently comorbid depression that can be considered a possible explanation for their cognitive dysfunction. We evaluated the cognitive performance of patients with CFS in comparison with a control group of healthy volunteers and a group of patients with major depressive disorder (MDD).

Patients and Methods: Twenty-five patients with CFS, 25 patients with major depressive disorder (MDD), and 25 healthy control subjects were given standardized tests of attention, working memory, and verbal and visual episodic memory, and were also tested for effects related to lack of effort/simulation, suggestibility, and fatigue.

Results:

• Patients with CFS had slower phasic alertness (speed in mentally processing the fact of an expected stimulus), and also had impaired working, visual and verbal episodic memory compared to controls.

• They were, however, no more sensitive than the other groups to suggestibility or to fatigue induced during the cognitive session.